Since the development of the computer, there are many electromechanical systems and devices which have been adapted for computer control. Typically, the computer includes a stored program and is interfaced with the electromechanical device through appropriate interface circuitry to monitor certain operating parameters and to control certain operating parameters of the device. Computers have been used to control single devices, and also to control a plurality of devices which might be spaced geographically.
With the advent of the microcomputer, and the dramatic decrease in cost and size, and the increase in flexibility and power, it has become feasible to automate and computerize many additional kinds of electromechanical devices. For example, computerized systems have been developed and are available in the prior art to control a number of irrigation systems, including center pivot irrigation systems, from a central base station, such as a farmer's house. A center pivot irrigation system generally comprises an elongated water pipeline with sprinklers spaced therealong with one end fixed at a central point about which the pipeline rotates, the sprinklers on the pipeline irrigating the land beneath it as the pipeline sweeps through a circular area. These elongated pipelines or center pivots can be as much as a quarter mile to a half mile long. Therefore, the distance between center pivot irrigation systems may be substantial as a farmer may own quite a number of these center pivot irrigation systems.
The computer based controls presently available in the prior art for center pivot irrigation systems are generally comprised of a central base station which contains a stored program which centrally controls the operation and monitoring of each of the center pivots linked to the base station. Typically, a communications link such as radio or telephone is provided to link the remote center pivot controls at the pivot points with the central computer. An interface and possibly some limited processing capability is provided at each remote location, but these remote processors typically follow the commands and timing determined by the central computer. This type of system can be thought of as a central master base station with slave units located at each pivot which follow the instructions of the master and which have no capability to independently operate the pivot.
At least one system in the prior art does provide a microcomputer in the remote control unit. However, as best understood, the microcomputer in the remote unit has as its principal task the handling of communications back and forth with the main base station, and the base station remains in full control of all of the functions of the remote unit and the center pivot irrigation system connected to it.
Although these systems in the prior art do provide central computer control of a number of geographically spaced irrigation systems, they do have some disadvantages. For example, if a pivot is to be turned on at some time in the future, typically the central computer stores that instruction and sends a command to turn the selected pivot on only at the time at which the turn-on is desired, and not at the time at which the instruction is entered to the computer. Therefore, if a turn-on time is requested for some time in the future, it is required that the computer be operational and the program be running at that time for the message to be transmitted and the control function to be achieved. This means that the farmer must be cognizant of these command times and ensure that the computer is operational and the program running at the time that these commands are to be executed.
Still another disadvantage is that for a large number of controlled irrigation systems, it may be required that more than just several of the systems be controlled at the same time, thereby resulting in delays in control for those systems near the end of the program execution. For example, a farmer with 100 center pivots may desire that 30 of them be turned on at about the same time. Under a central computer control, there can be an inordinate delay for the last ones of these 30 center pivots to be finally turned on. This results from the time lag required to communicate instructions between the central base station and the remote units. Typically, protocols would require some fixed amount of time to obtain a clear channel, transmit, acknowledge receipt of the transmission, and execute the instruction.
Still another disadvantage of the system of the prior art is that with central intelligence, the farmer is ultimately dependent upon the operation of a single computer. Although computers have become very reliable with increasing technology, it is not uncommon for failures to occur. With central intelligence, failure of the main computer shuts down the entire system resulting in manual control for all of the individual irrigation systems until the central computer is fixed. Should that happen, the farmer must manually control each of his irrigation systems through the pivot panel controls typically provided by manufacturers of irrigation systems which are highly reliable, but do not provide the programmable features inherent with computer control.
To solve these and other problems, and to provide a system with greatly enhanced reliability, flexibility, and ease of operation, the inventors herein have succeeded in developing a computer monitoring and control system which utilizes "intelligent remote units" at each irrigation system with a central computer for collecting and monitoring data transmitted from each of these intelligent remotes, and also having the capability of communicating desired instructions to these intelligent remotes for their processing and execution in accordance with the stored programs contained in each intelligent remote. This is a distributed logic or intelligence type of system in that each intelligent remote is a stand alone controller and can function fully independently of the base computer. To further enhance the versatility and flexibility of the system, the inventors have provided a system which permits a farmer to physically visit the remote unit, observe the operation of the irrigation system, enter any desired changes into the pivot panel with manual action, and then the system will indicate these changes back at the base station by generating an alarm message. Thus, a farmer may manually override the remote intelligent unit and enter changes directly as a result of having observed conditions at the location without having the system override his manual corrections.
At each pivot panel, a local/remote toggle switch is provided which can be used to disable the remote intelligent unit and prevent its control of the pivot panel and irrigation system.
By distributing the intelligence among the remote units, the system has freed itself from dependency upon the operation of the central computer. With the inventors' system as disclosed herein, should the central computer fail, each independent intelligent remote will continue to operate its associated center pivot irrigation system in accordance with the instructions stored therein. Still another advantage is that instructions requested by the base computer are immediately transmitted to the appropriate remote and stored in the remote's memory for execution at the designated time or other condition (either immediately or at some time in the future), the operator upon entering the instruction immediately knows whether the instruction has been transmitted and accepted by the remote unit and will hence be carried out. This eliminates the problems mentioned above with keeping the main computer operational to ensure execution of instructions at preselected times, and also concerns about the future operation of the computer to ensure future execution of present instructions. Additionally, instructions may be conditioned on other parameters for later execution.